Methods for making aluminum nitride armor bodies

ABSTRACT

A method of making aluminum nitride armor bodies is provided. The method starts with low cost bulk raw material, in the form of aluminum or aluminum alloy, cryogenically mills the raw material into a precursor powder, which is essentially free of oxides and other undesirable impurities. The precursor powder is formed into a pre-form using low cost, short residence time molding processes. Finally, the pre-form is exposed to a nitriding process to convert the pre-form into the aluminum nitride armor body. In this manner, the method avoids the use of high cost aluminum nitride as a starting material and avoids the need for the high cost, single axis densification processes of the prior art.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application Ser. No. 61/406,801, filed Oct. 26, 2010, the contents of which are incorporated by reference herein in their entirety.

BACKGROUND OF THE DISCLOSURE

1. Field of the Disclosure

The present disclosure relates to armor bodies such as, but not limited to, plates, bar shapes, and/or complex structures. More particularly, the present disclosure is related to methods for producing a low cost, high efficiency, high yield aluminum nitride material and forming armor bodies therefrom.

2. Description of Related Art

Armor bodies are often assembled into a protective panel or system, which have been used to protect buildings, vehicles (air, land, or water), and people from projectiles. When used to protect buildings, people, and vehicles, the armor plates have been made from variety of materials such as metal, ceramic, fiber composite, glass, and others materials.

Because of its low specific density, and attractive properties and ductility under very high strain rates and pressures, aluminum nitride (AlN) has long been of great interest for armor applications. The failure to apply aluminum nitride to armor has been the result of very high costs to fabricate aluminum nitride bodies.

Such costs are related to the current manufacturing methods which include first making aluminum nitride, converting this aluminum nitride into a powder, forming the aluminum nitride power into an aluminum nitride “pre-form”, and then consolidating the pre-form to full density by high temperature hot pressing using expensive tooling and processes (e.g., densification). This hot pressing is, in large part, required at temperatures in excess of 2,000 degrees Celsius and 2,000 pounds per square inch to overcome the sintering inhibitions caused by contaminations imparted by these precursor processing steps that make forming these covalent bonds so much more challenging.

By way of example, the aluminum nitride powders used as a starting material for such prior art processes are known to cost as much as $25 per pound. Further, the densification processes necessary to consolidate aluminum nitride pre-forms to a desired density are known to require the above pressures and temperatures with a residence time in the hot press of about 3 days including heating, sintering, and cooling. The high pressures required by such prior art densification processes have limited the molding to single axis moldings, which prevents complex shapes from being formed. The high cost of the starting raw material, combined with the high cost densification process, have made the aluminum nitride bodies made from such prior art processes prohibitively expensive for use in armor.

Accordingly, there is a continuing need for armor bodies of continuously decreasing weight, cost, and/or density, as well as continuously increasing threat protection.

BRIEF SUMMARY OF THE DISCLOSURE

The present disclosure provides a method that uses pure aluminum or aluminum alloys, which has a comparatively low bulk cost per pound, as a starting point of the process instead of using the high cost aluminum nitride powder of the prior art. The aluminum or aluminum alloy is then milled into a powder using a cryogenic milling process in a way that protects the powdered aluminum thus formed from oxidation. Once formed into a powder, the aluminum precursor is formed into a pre-form of a desired shape and size and the pre-form is subsequently exposed to a separate nitriding process, in which the pure aluminum or aluminum alloy pre-form is nitrided. Thus, the process of the present disclosure results in an aluminum nitride body, which starts with pure aluminum or aluminum alloy powder and lacks the expensive high temperature, high pressure densification process of the prior art.

The present disclosure provides a method to eliminate several processing steps and take a novel equiaxed aluminum powder, form it into the shapes desired for armor plating, and then, after formation into the desired shape, directly reacts the aluminum powder with nitrogen in a controlled exothermic reaction in a nitrogen atmosphere. The aluminum powder can, in some embodiments, be an aluminum alloy that contains desired sintering aids such as, but not limited to, rare earth metals, alkaline metals, and any combinations thereof. These alloys can also be selected to aid in sintering and/or aid in milling performance at cryogenic temperatures.

It has been found by the present disclosure that the use of aluminum as precursors for making armor requires that such a precursor be free of contamination with materials and elements with which these materials are naturally very reactive, such as oxygen, carbon, nitrogen, and iron, and results in a material that is very hard to sinter to full density as is required to make good armor. Because the bonds created by these contaminations are most all covalent bonds, these contaminants are nearly impossible to remove once they have joined. In many cases, the contaminant itself is difficult to measure and the negative effects are understood and recognized, but poorly quantified.

In the case of aluminum nitride the ability to make an aluminum nitride with no oxygen in the matrix through direct nitridation of a suitable equiaxed precursor has been determined by the present disclosure as one way to achieve low cost and high density.

The methods of the present disclosure provide an aluminum powder precursor which was more equiaxed, of a size between 400 nanometers and a few dozen microns, and free of oxygen. As such the aluminum powder precursor of the present disclosure is an important step to making the desired aluminum nitride armor bodies with respect to cost and to thermal conductivity.

In the methods of the present disclosure, aluminum lump or grain, of sufficient purity or composition suitable to the application being considered is selected. In some cases, the aluminum is alloyed with suitable rare earth metals, alkaline metals, and any combinations thereof. The selected material is milled such that there is exceptionally low to immeasurable levels of contamination and then these uncontaminated powders are processed directly into the desired shape of the armor body so that they are not further contaminated and are suitable for application inexpensively and with the desired properties. Finally, the shaped body is directly reacted with nitrogen in a controlled exothermic reaction in a nitrogen atmosphere.

In some embodiments, the starting aluminum material is milled in liquid nitrogen in a mill with a rotating shaft describing the Center Line ID or z axis of a cylindrical body and having a multitude of ceramic or ceramic lined rods attached orthogonally to the shaft. The shaft would rotate with force, “milling” the aluminum contained in the liquid nitrogen. The choice of liquid nitrogen or other suitable cryogenic liquid is based on the need to go to such low cryogenic temperatures so to make the materials brittle and capable of cryogenic milling.

When cryogenic milling in the presence of nitrogen, the powdered aluminum can be separated from the nitrogen at room temperature or a lower temperature and while being protecting with a cover to preclude oxidation and then can be formed into a compact pre-form. The aluminum pre-form is then reacted in a pressure vessel with controlled vapor pressure of nitrogen or dissociated ammonia to form aluminum nitride in situ.

Importantly, the formed aluminum nitride is a substantially pure, uncontaminated metal with a particle size, particle shape, and particle size distribution suitable for forming classic ceramic pre-forms with binders, in which case we desire a suitable “Green Density” in the desired range with minimal use of binders. In the case of these ceramics we desire to make a green density with a porosity which will allow the free flow of gas and reactants, and will result in the nitride reaction with the metal filling in the spaces towards theoretical density with little or no shrinkage of the pre-form.

In some embodiments, the aluminum of the pre-form has a density of 2.7 grams per cubic centimeter, while the aluminum nitride of the finished armor body has a density in the range of 3.3 grams per cubic centimeter such that the methods according to the present disclosure provide a green density of up to about 81%.

The methods according to the present disclosure control the direct reaction of the metal and the nitrogen due to its exothermic potential. The gas must have access to the internal interstices of the compact. The metal powder preferably is between 500 nanometers and 20 microns, and could be polymodal, to provide the ability to make the compact with limited removable binder. The binder is, preferably, selected from group of binders that do not leave residual carbon such as, but not limited to, pre-ceramic polymers.

The process in some embodiments of the present disclosure includes placing the aluminum into a grinding mill equipped with a center line powered shaft having a multitude of orthogonal bars, preferably made of or coated with or shielded with ceramics. Typically, the mill will be filled up to about 50% or more of its volume with each media and aluminum, to a level covering the upper bar. Then, liquid nitrogen will be poured in and the mill will be covered. Some of the nitrogen will sublime, further lowering the temperature of the liquid. Upon addition of the liquid nitrogen, the materials will to some degree thermal shock and upon rotation of the shaft, the thermal shock and transition from ductile to brittle materials will provide very quick attrition of the aluminum. Typically, the shaft will rotate between 50 and 400 RPM.

Advantageously, during the milling according to the present disclosure, the energy in the mill, or the attrition zone, is very low at the circumference and at the center of the mill near the shaft. Most of the attrition and energy is found in the middle of the orthogonal bars. In this case since the shaft, in a preferred embodiment the orthogonal shafts will be metal fitted with zirconia or silicon nitride covers, never comes into anything with strength, hardness or fracture toughness exceeding that of the brittle aluminum, there is little or no wear on the bars, and thus no contamination. The energy of the rotating bars crushes the aluminum autogenously, creating no contamination and quickly producing the particles size, distribution and shape and purity desired. It is to be expected that some intrinsic nitriding may occur during the milling process. However, such nitriding is merely an artifact of the milling process and does accounts for a small percentage of the aluminum precursor.

Upon separation from the nitrogen and with protection from oxygen or other contamination, a precursor as required for forming the armor body is provided. The precursor can be processed into a pre-form of a desired shape, which is then directly processed into aluminum nitride with low cost and net shape and high theoretical density by the reaction with nitrogen from net shape aluminum powder pre-forms made of this precursor in furnace operations that will control nitrogen to control the exothermic reaction typically with cross sections of 25 mm or less; or aluminum nitride in any desired ballistic protecting shape such as, but not limited to, plate, tile, sphere, or cylinder structures that can be used to construct armor systems; or aluminum nitride in complex or even honeycomb structures where the wall thicknesses are 25 mm or less.

The above-described and other features and advantages of the present disclosure will be appreciated and understood by those skilled in the art from the following detailed description, drawings, and appended claims.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a side, top perspective view of an armor body according to an exemplary embodiment of the present disclosure;

FIG. 2 is a flowchart showing an exemplary embodiment of a method for producing an armor body according to the present disclosure; and

FIG. 3 is a flowchart showing an alternate method for producing an armor body plate according to an exemplary embodiment of the present disclosure; and

FIG. 4 is a flowchart showing additional steps for producing a slurry in accordance with an exemplary embodiment of the method shown in FIG. 3.

DETAILED DESCRIPTION OF THE DISCLOSURE

Referring now to the drawings and in particular to FIG. 1, an exemplary embodiment of an armor body according to the present disclosure is shown and is generally referred to herein by reference numeral 10.

Advantageously, armor body 10 provides a light-weight energy absorbing projectile protection device capable of absorbing incoming projectile threats. Armor body 10 can find use in personal protection devices, vehicles, and buildings. For purposes of clarity, armor body 10 is shown in use on a vehicle 12, which is illustrated as a truck.

Of course, it is contemplated by the present disclosure for armor body 10 to find use on any vehicle 12 including, but not limited to, cars, boats, airplanes, watercraft, and any other vehicle that requires protection from threats. Further, it is contemplated by the present disclosure for armor body 10 to find use on any fixed or portable building or personal protection device. Although illustrated in plate or panel form, armor body 10 can have any desired shape or contour of a desired thickness 14.

A method for producing the armor body of FIG. 1 is disclosed herein and in the accompanying Figures.

FIG. 2 is a flowchart that shows one embodiment of the method for producing the armor body 10, or “method” 16. In the embodiment of FIG. 1, the method 16 includes a first step 18 where a precursor powder 20, which is essentially free of oxides and other undesirable impurities, including aluminum nitride, is obtained.

In one embodiment, the precursor powder 20 is made from substantially pure aluminum raw material 22. In another embodiment, raw material 22 for the precursor powder 20 is an aluminum alloy, the aluminum having been pre-alloyed with components such as rare earth metals, alkyl metals and combinations thereof, which serve to increase the millability of the precursor by increasing its brittleness, serve as sintering aids in later processing steps, serve as grinding media, otherwise improve the processability of the precursor, and any combinations thereof.

It has been determined by the present disclosure that the use of pure aluminum or aluminum alloy raw material 22, without the presence of significant amounts of aluminum nitride, as precursor powder 20 is an important aspect to reducing the cost of method 16.

In some embodiments, precursor powder 20 is formed by a cryogenic milling process 24 in which the pure aluminum or aluminum alloy raw material 22 is milled in the presence of a substantially inert liquid cover 26 that protects the raw material 22 from exposure to, and reaction with, outside contaminants, for example, contaminants in the atmosphere such as, but not limited to, water, air, and others. In this manner, precursor powder 20 can be formed so that it is substantially free of oxides and other undesirable impurities.

In some embodiments, inert liquid cover 26 is a cryogenic liquid such as liquid nitrogen, which serves to cool the raw material 22 prior to and during milling process 24, thereby increasing the brittleness of the raw material 22 and promoting diminution of the raw material 22 into precursor powder 20.

During cryogenic milling process 24 in the presence cover 26, it is understood that the aluminum or aluminum alloy raw material 22 may undergo some intrinsic nitriding. Specifically, it is understood that the aluminum or aluminum alloy raw material 22 may be exposed to conditions during milling process 24 that are sufficient to provide a native or intrinsic nitride layer to the milled precursor powder 20. These conditions include very high in situ temperatures of very small surface areas and volumes at the site of fracture during milling.

Without wishing to be bound by any particular theory, it is believed that such native or intrinsic nitriding merely forms a monolayer on the surface of the grains of precursor powder 20 with such levels of nitriding being insufficient to require the use of the prior art high pressure, high temperature densification processes described above. Thus, it is contemplated by the present disclosure for precursor powder 20 to have an aluminum nitride content of not more than a few angstroms thickness on only a portion of the surfaces.

Milling step 24 provides precursor powder 20 with a particle size between 400 nanometers and 50 microns.

Once precursor powder 20 is obtained, the precursor powder 20 is formed into a pre-form 28 of a desired shape during a molding step 30. When method 16 is used to form armor bodies, the pre-form 28 can have a plate-like or panel-like shape. Of course, it is contemplated by the present disclosure for pre-form 28 to have any shape suitable for the intended use of the armor body.

Since molding step 30 is merely forming precursor powder 20 into pre-form 28, the molding step 30 can be any room temperature forming process and can provide molding forces from multiple axes, which allows method 10 to provide complex, multi-axis molded shapes.

For example, molding step 30 can be a cold press process, a dry press process, a slip cast process, an injection molding process, an extrusion process, an isopressing process, and any combinations thereof. In some embodiments, precursor powder 20 can include sintering aids to assist in the formation of pre-form 30. The sintering aid can be pre-alloyed with raw material 22, or can be admixed with precursor powder 20 during milling step 24.

After pre-form 28 has been formed at molding step 30, the pre-form is then exposed to a reaction sintering or nitriding process 34 in a pressure vessel with controlled vapor pressure of nitrogen or dissociated ammonia to form aluminum nitride substrates in situ. Process 34 occurs at a temperature below the melting temperature of precursor powder 20, which allows for the sintering and nitriding of the precursor powder 20 without melting of the powder or pre-form 28. In addition to introducing the sinter aids by pre-alloying with the aluminum, sintering aids such as rare earth metals and alkali metals, can be introduced by controlling their partial pressures and enabling vapor phase transport and reaction in situ.

During nitriding step 32, nitrogen or dissociated ammonia flows into pores within pre-form 28 to result in a nitride reaction with the metal filling in the spaces towards theoretical density with little or no shrinkage of the pre-form. Thus, the thickness of pre-form 28, and hence of armor body 10, is dependent upon the ability of the reactant to flow through the pores of the pre-form 28. In some embodiments, pre-form 28 can have a maximum thickness 14 of about twenty-five millimeters (mm). In such reaction sintering processes 34, it has been found in our experience, for instance with silicon nitride, that bodies with cross sections more than about 25 mm tend to develop unreacted cores. It is contemplated by the present disclosure for armor body 10, if a thickness of greater than 25 mm is desired, to be assembled into a stack of a desired thickness.

Thus, method 16 starts with low cost bulk raw material 22 (i.e., aluminum or aluminum alloy), cryogenically mills the raw material 22 into the precursor powder 20, forms the precursor powder 20 into a pre-form 28 using low cost, short residence time molding processes, and converts the pre-form 28, via a nitriding process, into the AlN armor body 10. In this manner, method 16 avoids the use of high cost AlN as a starting material and avoids the need for the high cost densification processes of the prior art. Further, method 16 allows the molding step 30 to be a multi-axis molding process capable of complex shapes.

FIG. 3 is a flowchart that shows an alternate embodiment of the method for producing the armor body 10, or “method” 34. In the embodiment of FIG. 3, the method 34 includes producing a slurry 36 that includes (1) a precursor powder that is essentially free of oxides and other undesirable impurities and (2) a liquid that essentially prevents the oxidation of the precursor powder.

In at least one embodiment of the present disclosure, the liquid component of the slurry consists essentially of cryogenic liquid, and in one embodiment, the liquid component consists essentially of liquid nitrogen. In some cases a variant of the atmosphere can be a mixture of nitrogen and hydrogen, such as is obtained economically from disassociated ammonia, as this can provide a valuable reducing environment while providing good control over the nitrogen flow into the reaction.

FIG. 4 illustrates one embodiment of a method for producing the slurry 36. In the embodiment of FIG. 4, an aluminum precursor 38 is provided that is essentially free of oxides or other impurities detrimental to the efficient function of the armor body. In one embodiment, the precursor 38 is substantially pure aluminum. In another embodiment, the precursor 38 is an aluminum alloy, the precursor having been pre-alloyed with components such as rare earth and alkyl metals, which serve to increase the millability of the precursor by increasing its brittleness, serve as sintering aids in later processing steps, serve as grinding media, otherwise improve the processability of the precursor, and any combinations thereof.

A substantially inert liquid cover 40 is provided to substantially surround the precursor 38 and to protect the precursor from exposure to, and reaction with, outside contaminants, for example, contaminants in the atmosphere surrounding the precursor.

A mill is provided 42 which is capable of milling the precursor. The mill can be capable of milling the precursor 38 autogenously (i.e., without the need for grinding media) or, in other embodiments with grinding media selected to provide sintering aids.

In one embodiment, the mill comprises a substantially cylindrical vessel having an interior adapted to receive and contain the precursor 38, along with the inert cover 40 for essentially preventing oxidation of the precursor, and to limit exposure of the precursor and the inert cover to outside contaminants as shown in step 44. The central axis of the cylindrical vessel extends substantially upright, and a shaft extends along the central axis of the cylindrical vessel. A plurality of paddle members are fixed to and extend substantially orthogonally to the shaft within the cylindrical vessel interior, and a motor is secured to the shaft through suitable mechanical linkage so as to allow the motor to rotate the shaft and adjoined paddle members within the cylindrical vessel interior, thereby agitating precursor 38 within the cylindrical vessel to accomplish autogenous milling of the precursor into a powder at step 46 in cover 40.

In one embodiment, the shaft and paddle members, along with the interior of the cylindrical vessel, are formed from an inert ceramic material which is resistant to reaction with the precursor 38 during autogenous milling within the mill 42, and which is resistant to fracture or degradation during autogenous milling 46 within the mill. Thus, introduction of contaminants to the slurry 36 by the various components of the mill during autogenous milling 46 within the mill is limited. In another embodiment, the shaft, paddle members, and interior of the cylindrical vessel are formed primarily from a non-inert material, but are lined with the inert ceramic material.

The precursor 38 and the liquid cover 40 are placed in the mill interior at step 44. Thereafter, the shaft and adjoining paddle members are rotated within the mill thereby autogenously milling the precursor 30 within the mill interior at step 46, and thereby producing the slurry 36. In certain embodiments, a small amount of one or more sintering aids are added to the milling vessel 42 for aiding in binding the precursor 38 into the desired shape of the pre-form 28. It will be understood that, during the course of milling 46 the precursor, the cylindrical vessel of the mill 42 is sealed, and substantially all atmospheric contaminants are evacuated from the mill interior, thereby producing the slurry 36 in which the precursor powder is substantially free of oxides and other undesirable impurities.

It will further be understood that, in an embodiment in which an inert cryogenic liquid 40, such as liquid nitrogen, is used as the liquid cover, the cryogenic liquid serves to cool the precursor prior to and during milling 46, thereby increasing the brittleness of the precursor 38 and promoting diminution of the precursor into powder. As well, grinding media, typically of a smaller size than one of ordinary skill in the art would use in a traditional mill will be used to fill about half the volume of the mill up to that level covering the top paddle and the paddles in energetic rotation will cause this media to perform most of the attrition in that volume of the mill starting from the shaft and extending to about three quarters of the way to the wall. There is very little milling action at the wall of the mill.

During milling 46, it is understood that the aluminum or aluminum alloy precursor 38 may undergo some intrinsic nitriding. Specifically, it is understood that the aluminum or aluminum alloy precursor 38 may be exposed to conditions within the milling step 46 that are sufficient to provide a native nitride layer to the milled grains. However, such native or intrinsic nitriding merely forms a monolayer on the surface of the aluminum grains, which has been determined by the present disclosure to not be sufficient to require the use of the prior art high pressure, high temperature densification processes described above.

Referring again to FIG. 3, a mold is provided at step 48 having an interior substantially conforming to a desired shape of the armor body 10 to be produced. At an optional step 50, a delaminating layer is applied to an interior surface of the mold in order to allow the “green” armor body (e.g., pre-form 28) to be easily released from the interior of the mold.

Following production of the slurry 36, the slurry is introduced into the interior of the mold at step 52. In an optional step, the liquid cover 40 is replaced with a second inert cover at step 54.

In one embodiment in which liquid nitrogen is used as the liquid cover 40, the liquid nitrogen is warmed above its boiling point in the presence of argon gas, thereby allowing the liquid nitrogen to evaporate and separate from the precursor 38, thereby replacing the liquid nitrogen liquid cover with the argon gas second inert cover 54.

Once the slurry 36 is introduced into the interior of the mold at step 52, the precursor 38 is precipitated from the slurry 36 to form the pre-form 28 of the armor body 10 within the mold at step 56. In one embodiment, the liquid component of the slurry 36 is evaporated to encourage the precipitation of the precursor powder 38 from the slurry 36.

In another embodiment of the present invention, as shown in optional step 58 of FIG. 3, the mold is vibrated to encourage the deposition of a uniform layer of the precursor powder 38 along the bottom interior portion of the mold.

In another embodiment, the aluminum precursor 38 can be separated from the nitrogen cover 40 at room temperature or a lower temperature and protected with a cover to preclude oxidation. Next, the aluminum precursor 38 can be compacted into the pre-form 28 using any known dry press or cold press technique such as, but not limited to, slip casting or injection molding at step 60.

Once the pre-form 28 has been formed at step 60, the pre-form is exposed to a nitriding process 62. For example, pre-form 27 can be placed in a pressure vessel with controlled vapor pressure of nitrogen or dissociated ammonia to form aluminum nitride substrates in situ. In addition to introducing the sinter aids by pre-alloying with the aluminum, sintering aids such as rare earth metals and alkali metals, can be introduced by controlling their partial pressures and enabling vapor phase transport and reaction in situ.

It will be understood that in addition to evaporation or in alternative to evaporation, freeze casting can be used to accomplish precipitation of the precursor powder 38 from the slurry 36 at step 56, thus further limiting oxidation of the precursor powder. It will further be understood that other methods and techniques may be used accomplish precipitation of the precursor powder 38 from the slurry 36 at step 56 to form the pre-form 28 without departing from the spirit and scope of the present disclosure.

While the present disclosure has been described with reference to one or more exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope thereof. In addition, modifications may be made to adapt a particular situation or material to the teachings of the disclosure without departing from the scope thereof. Therefore, it is intended that the present disclosure not be limited to the particular embodiment(s) disclosed as the best mode contemplated, but that the disclosure will include all embodiments falling within the scope of the appended claims. 

1. A method of making an aluminum nitride armor body, comprising: obtaining a precursor powder of pure aluminum or aluminum alloy that is essentially free of oxides and nitrides; forming the precursor powder into a pre-form having a desired shape of the armor body; and exposing the pre-form to a nitriding process to form the aluminum nitride armor body.
 2. The method of claim 1, wherein the step of obtaining the precursor powder comprises: selecting a raw material comprising substantially pure aluminum or an aluminum alloy; and cryogenically milling the raw material in the presence of a substantially inert liquid cover to protect the raw material from exposure to, and reaction with, outside contaminants to a desired particle size.
 3. The method of claim 2, wherein the liquid cover comprises cryogenic liquid.
 4. The method of claim 4, wherein the liquid cover comprises liquid nitrogen.
 5. The method of claim 2, wherein the raw material is an aluminum alloy pre-alloyed with rare earth, alkyl metals, and any combinations thereof.
 6. The method of claim 2, wherein the desired particle size is between 400 nanometers and 50 microns.
 7. The method of claim 1, wherein the step of forming the precursor powder into the pre-form comprises a room temperature forming process.
 8. The method of claim 1, wherein the step of forming the precursor powder into the pre-form comprises multi-axis forming process.
 9. The method of claim 1, wherein the step of forming the precursor powder into the pre-form comprises a molding process selected from the group consisting of a cold press process, a dry press process, a slip cast process, an injection molding process, an extrusion process, an isopressing process, and any combinations thereof.
 10. The method of claim 1, wherein the desired shape comprises a plate-like or panel-like shape.
 11. The method of claim 1, wherein the step of exposing the pre-form to the nitriding process comprises exposing the pre-form, in a pressure vessel, with controlled vapor pressure of nitrogen or dissociated ammonia.
 12. The method of claim 11, wherein the nitrogen or dissociated ammonia flows into pores within the pre-form to result in a nitride reaction filling in the pores towards theoretical density with substantially no shrinkage of the pre-form.
 13. The method of claim 12, wherein the desired shape has a maximum thickness of about 25 millimeters.
 14. A method of making an aluminum nitride armor body, comprising: producing a slurry having a precursor powder that is essentially free of oxides and other undesirable impurities and a cover liquid that essentially prevents the oxidation of the precursor powder, the precursor powder comprises pure aluminum or aluminum alloy; introducing the slurry into an interior of a mold having a desired shape; precipitating the precursor powder from the slurry to form a pre-form having the desired shape; and placing the pre-form in a pressure vessel with controlled vapor pressure of nitrogen or dissociated ammonia to form aluminum nitride in the pre-form.
 15. The method of claim 14, wherein the precursor powder comprises aluminum alloyed with rare earth metal, alkyl metal, and combinations thereof.
 16. The method of claim 14, wherein the step of producing the slurry comprises milling a raw material of pure aluminum or aluminum alloy with the cover liquid in an evacuated mill.
 17. The method of claim 14, further comprising applying a delaminating layer to an interior surface of the mold before introducing the slurry into the interior of the mold.
 18. The method of claim 14, further comprising replacing the cover liquid with a second inert cover in the mold by warming the cover liquid above its boiling point in the presence of the second inert cover, thereby allowing the cover liquid to evaporate and separate from the precursor powder.
 19. The method of claim 14, further comprising vibrating the mold to encourage deposition of a uniform layer of the precursor powder along a bottom interior portion of the mold.
 20. A method of making an aluminum nitride armor body, comprising: producing a slurry having a precursor powder that is essentially free of oxides and other undesirable impurities and a cover liquid that essentially prevents the oxidation of the precursor powder, the precursor powder comprises pure aluminum or aluminum alloy; separating the precursor powder from the slurry and covering the precursor powder to preclude oxidation; compacting the precursor powder into a pre-form having a desired shape; and placing the pre-form in a pressure vessel with controlled vapor pressure of nitrogen or dissociated ammonia to form aluminum nitride in the pre-form. 